07 December 2010

Flood Losses in Africa

A recent and important paper in GRL discussed the role of climate in the observed increase in African flood losses over the past century. The paper concluded that climate has had an inconsequential role -- from the paper:

Based on the results of both continental and at‐site analyses, we find that the magnitude of African floods has not significantly increased during the Twentieth Century (Figures 2 and 3), and that climate has not been a consequential factor in the observed increase in flood damage. This is consistent with the results previously obtained [Kundzewicz et al., 2005; Bates et al., 2008; Petrow and Merz, 2009; Lins and Slack, 1999; Mudelsee et al., 2003] in different areas, such as North America, Europe, and Australia.

So if floods haven't increased, the cause of increasing damage must lie in factors other than climate:

. . . the intensive and unplanned urbanization in Africa and the related increase of people living in floodplains [Hardoy et al., 2001; Douglas et al., 2008] has led to an increase in the potential adverse consequences of floods and, in particular, of the most serious and irreversible type of consequence, namely the loss of human lives [Jonkman, 2005]. This can be shown, at the continental scale, by analyzing the dynamic of African population and the most recent deadly floods. For instance, Figure 4 shows the spatial distribution of population growth [Nelson, 2010] and the location of the latest floods, and deadly floods, in Africa (Dartmouth Flood Observatory, Global Archive of Large Flood Events, 2010). It can be seen that most of the recent deadly floods have happened where the population has increased more.